<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>字符串大小写转换</title>
    <script>
    function deal(opt){
        var str=document.getElementById('old').value;
        switch (opt){
            case 'upper':
            str=str.toUpperCase();
            break;
            case 'lower':
            str=str.toLowerCase();
            break;
        }
        document.getElementById('new').value=str;
    }
    </script>
</head>
<body>
    <h2>大小写转换</h2>
   <p> 原数据：<input type="text" id="old"></p>
   <p> 操作：</p>
   <p><input type="button" value="转大写" onclick="deal('upper')">
    <input type="button" value="转小写" onclick="deal('lower')"></p>
    <p>新数据: <input type="text" id="new"></p>
    <p><a href="4.html">返回上一页</a></p>
</body>
</html>